Magnetically-controllable, semi-active haptic interface system and apparatus

ABSTRACT

A haptic interface system or force feedback system having a magnetically-controllable device that provides resistance forces opposing movement. The magnetically-controllable device is adapted for use with a force feedback computer system to provide force feedback sensations to the system&#39;s operator. The magnetically-controllable device contains a magnetically-controllable medium beneficially providing variable resistance forces in proportion to the strength of an applied magnetic field. The system further comprises a controller that executes an interactive program or event, a video display, and a haptic interface device (e.g. joystick, steering wheel) in operable contact with an operator for controlling inputs and responses to the interactive program. Based on the received inputs and on processing the program, the controller provides a variable output signal, corresponding to a feedback force, to control the magnetically-controllable device for providing dissipative resistance forces to oppose the movement of the haptic interface device and to provide the operator with a force feedback sensation.

CROSS REFERENCE COPENDING APPLICATION

The present application is a continuation-in-part application ofcopending U.S. patent application Ser. No. 09/189,487, filed Nov. 10,1998.

FIELD OF THE INVENTION

The present invention relates generally to a haptic interface system forproviding force feedback sensations, and more particularly, to a hapticinterface system employing a magnetically-controllable medium to provideresistance forces.

BACKGROUND

Haptic interface systems, also known as force feedback systems, providean operator holding an interface device, such as a joystick or steeringdevice, with “feel” or tactile sensations in response to whatever isbeing controlled by the interface device. The haptic interface system isoften used for controlling the steering and operation of vehicles andmachinery. Frequently such devices are used in combination with acomputer game. In such a game, the action on a video display and themovement of a joystick or steering device are coordinated with physicalforce imparted to the operator's hand through the joystick or steeringdevice, to provide a simulated “feel” for events happening on thedisplay. For example, in an auto racing game, when an operator steers acar around a sharp turn at high speed, the haptic interface systemimparts force on the steering wheel to make it more difficult to turnthe wheel into the curve. This force feedback simulates the centrifugalforce of the car making the turn and the friction forces applied to thetires as they are turned. Thus, haptic interface systems provide remotesimulation of the actual physical feeling associated with an action orevent through force feedback.

Typical haptic interface systems include one or more motors connected tothe interface device in order to impart the force feedback sensation.Typical motors include direct current (DC) stepper motors andservo-motors. If the interface device is a joystick, motors are used toimpart force in an x-direction, in a y-direction, or in combination toprovide force in any direction that the joystick may be moved.Similarly, if the interface device is a steering wheel, motors are usedto impart rotational force in a clockwise or counterclockwise direction.Thus, motors are used to impart forces in any direction that theinterface device may be moved.

In a system using a single motor, the motor may be connected to theinterface device through a gear train, or other similar energy transferdevice, in order to provide force in more than one direction. In orderto enable one motor to be used in a system, a reversible motor istypically utilized to provide force in two different directions.Additionally, mechanisms are required to engage and disengage thevarious gears or energy transfer devices to provide force in the properdirection at the proper time. In contrast, other typical systems usemore than one motor to provide force in the required directions. Thus,current systems utilize a number of differing approaches to handle thedelivery of force feedback sensations.

Current haptic interface systems may be disadvantageous, however, for anumber of reasons. One primary area of concern is the cost of suchsystems. One item greatly contributing to the cost of a typical systemis the use of DC stepper and servo-motors, and reversible motors. Thesetypes of motors are very sophisticated, requiring the ability to changespeeds or rotations per minute (rpm), maintain different speeds, andreverse rotational direction. These features require greater mechanicaland electrical complexity, which equates to a comparatively very highcost. Further, these motors need to be small in size in order to keepthe haptic interface system from becoming unwieldy. This additionallycomplicates their design and increases cost. Also, because of theirrelatively small size, the sophisticated motors typically required in ahaptic interface system are only able to generate a limited amount oftorque. As such, the operator of an interface device may easily be ableto overcome the torque or force feedback supplied by the motor. Thus,providing a small, sophisticated motor for a haptic interface system isrelatively very costly, and may result in insufficient force feedback.

Also disadvantageously, typical DC motors used in haptic interfacesystems are not designed to perform in the manner required by thesystem. In order to provide force feedback, typical systems use directdrive motors configured to mechanically engage the output shaft of themotor with the interface device. For example, the output shaft of a DCmotor may be geared to a steering wheel shaft or linked to a slide orother mechanism controlling the movement of a joystick. When the motorengages the gear or slide, the motor drives the interface device toprovide force feedback. The operator holding the interface device,however, typically opposes the force feedback. The opposing forcesupplied by the operator then works against the direction of the motoroutput, which tends to stall the motor. Not only does this opposingforce tend to wear out and/or strip components within the motor, but thestall condition leads to the generation of higher electric currentswithin the motor, straining the electrical components in the motor. Dueto the repetitious nature of a haptic interface system, the reliabilityand longevity of motors in such haptic interface systems are severelyreduced. Thus, motors used in typical haptic interface systems aretypically not very well suited for the demanding environment in whichthey are operated.

Yet another disadvantage of current commercial haptic interface systemsis that high impact forces from a motor connected to an interface devicemay be dangerous for the operator of the interface device. When thehaptic interface system requires a quick, high impact force, a motorconnected to an interface device may respond with a large force that mayinjure the operator if the operator is not ready for the abrupt force.This may be accounted for by ramping up the speed of the motor toachieve the force, but then the sensation becomes less realistic.Further, varying the engagement speeds of the motor complicates thesoftware program that is used to run the haptic interface system,thereby further increasing cost. Thus, producing a realistic-feelinghigh impact force with current haptic interface systems may be dangerousto the operator or may require costly and complex system programming.

Some prior art devices have attempted to overcome some of the drawbacksof current haptic interface systems, with limited results. Anelectrorheological (ER) actuator, utilized in a force display system, isproposed by J. Furusho and M. Sakaguchi entitled “New Actuators Using ERFluid And Their Applications To Force Display Devices In Virtual RealitySystems,” in abstracts of the International Conference On ER Fluids, MRSuspensions and their Applications, Jul. 22-25, 1997 Yonezawa, Japan,pg. 51-52. An ER actuator comprises a device that contains an ER fluid,which is a substance that changes its shear strength with application ofan electric field. The ER fluid can then be used as a clutch or a braketo increase resistance between two members.

The use of such an ER actuator is severely disadvantageous, however, foruse in typical haptic interface systems. One major issue is that an ERactuator presents a major safety problem because of the high electricvoltage required to produce the electric field necessary to generate adesired change in shear strength in the ER fluid. For a haptic interfacesystem, a typical ER fluid actuator may require voltages in the range ofabout 1000 to 5000 volts. Conversely, the motors used in the typicalsystems described above require in the range of about 500 milliamps (mA)to 1.0 A of current. Thus, the voltage required to operate an ERactuator is very high, making an ER actuator undesirable, and possiblyunsafe, for a consumer device subject to a great amount of wear andtear.

Additionally, an ER actuator detrimentally requires expensive seals tohold the ER fluid within cavities within the actuator. Seals frequentlywear, causing reliability problems for ER actuators and concerns aboutER fluid leaks. Further, the use of seals typically requires machinedparts having tight tolerances, additionally increasing the cost of theER actuator. Also, ER actuators require expensive bearings to insure therelative positioning of the tight-tolerance parts.

Similarly, precise machining is required for the internal rotatingcomponents of an ER actuator, further increasing the cost of theactuator. Because an ER device requires a relatively large amount ofsurface area between the ER fluid and the two members that the ER fluidcontacts, tight tolerance machining is needed between the multiple,adjacent surfaces of the members. Thus, a relatively large amount ofsurface area may be required to generate sufficient torque to providethe levels of force feedback required by typical haptic interfacesystems.

Finally, typical ER actuators that provide appropriate force may be toolarge to be integrated into a commercial haptic interface system. Thedevice utilized to provide force feedback in a typical haptic interfacesystem must be small and lightweight in order to be practicallyintegrated into the system. An ER actuator meeting these requirements isvery costly to produce, besides having the above-stated deficiencies.Thus, utilization of an ER actuator in a typical haptic interface systemis not desirable.

Therefore, it is desirable to provide a haptic interface system that ismore simple, cost-effective, reliable and better performing than theabove-stated prior art.

SUMMARY OF THE INVENTION

According to a preferred embodiment of the present invention, a hapticinterface system of the present invention comprises amagnetically-controllable device that advantageously provides a variableresistance force that opposes movement of a haptic interface device toprovide force feedback sensations. The haptic interface device is inoperative contact with the operator of a vehicle, machine or computersystem. The magnetically-controllable device beneficially comprises amagnetically-controllable medium between a first and second member,where the second member is in communication with the haptic interfacedevice. For purposes of this description, the magnetically controllablemedium shall include any magnetically controllable material such as amagnetorheological fluid or powder. The magnetically-controllable mediumprovides the variable resistance force, in proportion to the strength ofan applied magnetic field, that opposes relative movement between thefirst and second members. The haptic interface system of the presentinvention may be used to control vehicle steering, throttling, clutchingand braking; computer simulations; machinery motion and functionality.Examples of vehicles and machinery that might include the hapticinterface system of the present invention comprise industrial vehiclesand watercraft, overhead cranes, trucks, automobiles, and robots. Thehaptic interface device may comprise, but shall not be limited to asteering wheel, crank, foot pedal, knob, mouse, joystick and lever.

Furthermore, the controller may send signals to the vehicle, machine orcomputer simulation 30 in response to information obtained by sensor 32and other inputs 30 for purposes of controlling the operation of thevehicle, machine or computer simulation. See FIGS. 1A and 1B. Once theoperator inputs and other inputs are processed by micrprocessor 54, aforce feedback signal is sent to the magnetically controllable device 24which in turn controls the haptic interface 26 such as a joystick,steering wheel, mouse or the like to reflect the control of the vehicle,machine or computer simulation.

The system additionally comprises a controller, such as a computersystem, adapted to run an interactive program and a sensor that detectsthe position of the haptic interface device and provides a correspondingvariable input signal to the controller.

The controller processes the interactive program, and the variable inputsignal from the sensor, and provides a variable output signalcorresponding to a semi-active, variable resistance force that providesthe operator with tactile sensations as computed by the the interactiveprogram. The variable output signal energizes a magnetic fieldgenerating device, disposed adjacent to the first and second members, toproduce a magnetic field having a strength proportional to the variableresistance force. The magnetic field is applied across themagnetically-controllable medium, which is disposed in a working spacebetween the first and second members. The applied magnetic field changesthe resistance force of the magnetically-controllable medium associatedwith relative movement, such as linear, rotational or curvilinearmotion, between the first and second members in communication with thehaptic interface device. As such, the variable output signal from thecontroller controls the strength of the applied magnetic field, andhence the variable resistance force of the magnetically-controllablemedium. The resistance force provided by energizing themagnetically-controllable medium controls the ease of movement of thehaptic interface device among a plurality of positions. Thus, thepresent haptic interface system provides an operator of a vehicle,machine, or computer simulation, force feedback sensations through themagnetically-controllable device that opposes the movement of the hapticinterface device.

In a preferred embodiment, the magnetically-controllable medium withinthe magnetically-controllable device is contained by an absorbentelement disposed between the first and second member. The absorbentelement may be compressed from a resting state, preferably in the amountof about 30%-70% of the resting state. The absorbent element may beformed as a matrix structure having open spaces for retaining themagnetically-controllable medium. Suitable materials for the absorbentelement comprise open-celled foam, such as from a polyurethane material,among others.

The magnetically-controllable medium is a medium having a shear strengththat varies in response to the strength of an applied magnetic field.One preferred type of magnetically-controllable medium is amagnetorheological fluid. As mentioned above, the magnetic-fieldgenerating device provides the applied magnetic field. Themagnetic-field generating device is preferably a coil and comprises awire having a number of turns and a certain gauge. The number of turnsand gauge of the wire are dependent upon the desired range of thevariable strength magnetic field and upon the electric current andvoltage of the variable output signal.

As previously indicated hereinabove, the controller may comprise acomputer system further comprising a host computer, a control unit andan amplifier. The control unit and amplifier, as is explained below, mayalternatively be separate components or part of a haptic interface unit.The host computer comprises a processor that runs the interactiveprogram. The control unit comprises a microprocessor and firmware thatare used to modify the variable input signal received from the sensorand the variable output signal received from the host computer. Thecontrol unit then provides a modified variable input signal to the hostcomputer and a modified variable output signal to themagnetically-controllable device. The modification function performed bythe control unit enables communication between the host computer and themagnetically-controllable device and the sensor. The amplifier furthermodifies the output signal to provide an amplified variable outputsignal in situations where the output signal from host computer is notsufficient to control the magnetically-controllable device. Further, thecontrol unit and amplifier may act as local processors, reducing theburden on the host computer by providing output signals for certaininput signals, such as to provide reflex-like resistance forces, that donot need to be processed by the host computer.

In one embodiment, the present invention discloses a haptic interfaceunit comprising the magnetically-controllable device, as describedabove, is adapted to provide a variable resistance force in proportionto a received variable output signal generated by a computer systemprocessing an interactive program. The magnetically-controllable devicefurther comprises a magnetic-field generating device, first and secondmembers, and a magnetically-controllable medium. The magnetic-fieldgenerating device is energizable by the variable output signal toprovide a variable strength magnetic field. The first and second membersare adjacent to the magnetic field generating device. Themagnetically-controllable medium is disposed between the first andsecond members, where the magnetically-controllable medium provides thevariable resistance force in response to the variable strength magneticfield. Additionally, the haptic interface unit may further comprise ahaptic interface device, adapted to be in operable contact with theoperator, for controlling and responding to the interactive program. Thehaptic interface device is in communication with themagnetically-controllable device and has a plurality of positions,wherein an ease of movement of the haptic interface device among theplurality of positions is controlled by the variable resistance force.Finally, the haptic interface unit may further comprise a control unitthat provides a signal to the magnetically-controllable device tocontrol the variable resistance force.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic block representation of the haptic interfacesystem according to the present invention.

FIG. 1B is a schematic block representation of a haptic interface systemaccording to the present invention for use in a computer simulationapplication.

FIG. 1C is a schematic block representation of a haptic interface systemaccording to the present invention for use in a vehicle or machinesteering application.

FIG. 1D is a schematic block representation of a haptic interface systemaccording to the present invention for use in a vehicle or machinejoystick application.

FIGS. 2A-2B are a perspective view and a cross-sectional view,respectively, of a typical magnetically-controllable device.

FIG. 3 is a partial cross-sectional view of one embodiment of a hapticinterface unit.

FIG. 4a is a cross-sectional view along line 4—4 in FIG. 3 of oneembodiment of a magnetically-controllable device.

FIG. 4b is a cross-sectional view of an alternate embodiment of amagnetically-controllable device.

FIG. 5 is a partial cross-sectional rear view of another embodiment of ahaptic interface unit, with some components removed for clarity,utilizing the magnetically-controllable device of FIGS. 3 and 4.

FIG. 6 is a partial cross-sectional side view of the haptic interfaceunit of FIG. 5, with some components removed for clarity.

FIG. 7a is a partial cross-sectional top view taken along line 7 a—7 aof FIG. 5, with some components removed for clarity.

FIG. 7b is a top view of the sensor which interconnects to the plates ofFIG. 7a;

FIG. 8a is a perspective view of yet another embodiment of a hapticinterface unit.

FIG. 8b is a side view of the rack of FIG. 8a.

FIG. 9 is a side view of yet another embodiment of amagnetically-controllable device.

FIG. 10 is a cross-sectional view along line 10—10 of the device in FIG.9.

FIG. 11 is a cross-sectional view of another embodiment of amagnetically-controllable device.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention a semi-active haptic interface system20 is illustrated schematically in FIG. 1A. The semi-active hapticinterface system 20 provides resistance forces to an operator 22 andcomprises a magnetically-controllable device 24 that imparts forcefeedback resistance sensations to the operator through a hapticinterface device 26 by opposing the movement of the haptic interfacedevice. Operator 22 moves haptic interface device 26 to control andrespond to a control program or algorithm executed by the controller 28.Signals relating to the application where the system is located such asa vehicle, machine or computer simulation are sent by the output device30 to controller 28 where they are processed in order to determine therequired effect on magnetically-controllable device 24. The outputdevice may comprise a monitor, with corresponding images displayed onthe monitor 30. A sensor 32 detects the movements of haptic interfacedevice 26 and reports the movements to controller 28. The controller 28for purposes of the description of the preferred embodiment of theinvention is a computer system 28 that interactively responds bygenerating new images on monitor 30 and by controllingmagnetically-controllable device 24 to provide a variable resistanceforce corresponding to the movement of haptic interface device 26 andcorresponding to the images on the monitor 30. Thus, haptic interfacesystem 20, and particularly magnetically-controllable device 26,advantageously provide a simple, cost-effective, high-performancesolution for supplying a semi-active resistance force enabling operator22 to feel realistic force feedback sensations.

When the system is installed in a vehicle or machine the system may notinclude a monitor. The monitor would be included in a computersimulation application of the invention as shown in FIG. 1B.

The semi-active feature of haptic interface system 20 of the presentinvention is particularly beneficial in providing a very cost-efficient,compact and robust system. As used herein, the term “semi-active” refersto the ability to provide a dissipative opposing resistance force inresponse to an applied motion. In contrast to prior art haptic interfacesystems that provide “active” force feedback utilizing expensive motors,haptic interface system 20 of the present invention advantageouslyutilizes magnetically-controllable device 24 including a magneticallycontrollable medium 34 (FIG. 2A) to provide semi-active, variableresistance forces. The term “active” refers to the ability toindependently impart a force to the haptic interface device withoutrequiring the operator to move the device. Through continual feedbackbetween haptic interface device 26 and controller 28, the controllerdirects magnetically-controllable device 24 to provide variableresistance forces that oppose the movement of the haptic interfacedevice 26. Further, based on running the interactive program, controller28 directs the resistance provided by magnetically-controllable device24 to vary in conjunction with images on display 30 and/or with themovement of the haptic interface device 26.

For example, if the operator is controlling a computer simulation ofFIG. 1B such as a race car driving interactive program, and operator 22attempts to move haptic interface device 26 in a direction that steersthe car into a non-destructible wall, then the computer system willprovide a control signal. The signal controls magnetically-controllabledevice 24 to provide resistance forces equal to or greater than theforce applied to the haptic interface device by the operator. Thisopposes any movement of the haptic interface device and simulating thefeel of driving into an immovable wall.

Similarly, given the same interactive race car driving program andoperator 22 driving the car around a curve, controller 28 provides avariable amount of resistance force less than the force applied byoperator 22 to haptic interface device 26 to simulate the actualcentrifugal and friction forces. The amount of the variable resistanceforce depends upon the speed and traction of the car and the sharpnessof the curve, for example. As a result, magnetically-controllable device24 creates resistance force feedback sensations felt by operator 22through haptic interface device 26, giving the interactive program arealistic feel. Thus, as operator 22 maneuvers haptic interface device26, the system of the present invention supplies resistance to opposethe motion of the haptic interface device to simulate real-life forces.As indicated hereinabove, the haptic interface system of the presentinvention may be used to control vehicle steering, throttling andbraking; computer simulations; machinery motion and functionality.However as the description of the haptic interface system of the presentinvention proceeds, for purposes of describing the operation of theinvention the system will be used to control computer simulations.Schematic representations of the system 20 integrated in thevehicle/machine steering wheel or joystick are shown in FIGS. 1C and 1D.

Magnetically-controllable device 24 beneficially contributes to thecost-efficient, compact and robust design of haptic interface system 20.Referring to FIGS. 2A and 2B, a typical magnetically-controllable device24 generally comprises a magnetically-controllable medium 34 containedin a working space 36 between first member 38 and second member 40.Members 38, 40 are disposed for relative movement along the matingsurfaces, such as linear or rotational motion as indicated by thearrows. Magnetically-controllable medium 34 is under the influence of anannular-shaped magnetic-field generating device 42 (FIG. 2B) energizableto produce a variable strength magnetic field across the medium.Magnetically-controllable medium 34 is a medium that has a shearstrength that changes in proportion to the strength of an appliedmagnetic field. In other words, the “apparent viscosity” of the mediumchanges proportionally with the strength of an applied magnetic field,providing controllable shear force to resist relative movement betweenmembers 38, 40.

A suitable magnetically-controllable medium 34 may comprisemagnetorheological fluids such as described in commonly assigned U.S.Pat. Nos. 5,683,615 and 5,705,085 hereby incorporated by reference.Other fluids, such as carbonyl iron dispersed in hydrocarbon oil, or andany medium exhibiting a change in properties in response to an appliedmagnetic field. Other magnetorheological fluids which may be used in thepresent invention are disclosed in, for example, U.S. Pat. No. 5,382,373to Carlson et al. and U.S. Pat. No. 5,578,238 to Weiss, et al., herebyincorporated by reference.

First 38 and second 40 members are adjacent to magnetic-field generatingdevice 42, and disposed at least partially on opposing sides ofmagnetically-controllable medium 34. Members 38, 40 each preferablyinclude a highly magnetically permeable material, such as a magneticallysoft steel such as AISI 1010, AISI 1018 or AISI 12L14 in order to act aspole pieces to produce a magnetic field across medium 34, as indicatedby flux lines 44. Additionally, second member 40 is in communicationwith haptic interface device 26, such that operator 22 moving the hapticinterface device during energization of magnetic-field generating device42 feels the changed resistance force generated between first 38 andsecond 40 members by magnetically-controllable medium 34. Significantshear force resisting the relative movement of first member 38 andsecond member 40 can advantageously be obtained with a small amount ofmagnetically-controllable medium 34 between movable members 38, 40.Thus, a variety of relative movements, such as linear, rotational,curvilinear, and pivoting, that include shear movement between twomembers can be controlled by a magnetically-controllable deviceaccording to the present invention.

Additionally, magnetically-controllable device 24 preferably containssubstantially the entire amount of magnetically-controllable medium 34at working space 36. Any suitable means for containing medium 34 atworking space 36 can be used. According to a preferred embodiment of theinvention, means for containing magnetically-controllable medium 34within working space 36 comprises an absorbent element 46. Absorbentelement 46 is a material that can take up and holdmagnetically-controllable medium 34, for example by wicking or capillaryaction. Absorbent element 46, disposed between first member 38 andsecond member 40, preferably has a matrix structure with open spaces forretaining magnetically-controllable medium 34. Whilemagnetically-controllable medium 34 is held within the spaces inabsorbent element 46, the material itself may or may not be absorbent. Acomplete description of such devices may be found in U.S. patentapplication Ser. No. 08/959,775 to Carlson filed Oct. 29, 1997 entitled“Controllable Medium Device And Apparatus Utilizing Same.”

A particularly preferred absorbent element 46 is a sponge-like material,for example, an open-celled foam or partly open-celled foam. Suitablematerials for making such a foam comprise polyurethane, rubber, siliconerubber, polyamide, neoprene, loner, melamine, polyimide high temperaturefoam, and metal foam. Additionally, other exemplary absorbent materialsinclude felts, including felts mad of material such as Nomex® aramidfiber, polybenzimadazole fiber, Teflon® fiber and Gore-Tex® fiber,fiberglass wicking, and woven brake or clutch lining material. Othermaterials and structures are also suitable, such as a metal mesh, abrush, or a flocked surface material.

Absorbent element 46 also beneficially allows for reduced tolerancesbetween the components of magnetically-controllable device 24, therebyreducing the cost to manufacture and assemble device 24. In order tonegate the affects of wear at the surface of absorbent element 46, andto provide a robust design, it is desirable to have the materialcompressed between member 38, 40. Absorbent element 46 may be utilizedwithout any compression, but the material is preferably compressedbetween about 30% and 70% from a resting state to its installed state.Thus, by containing substantially the entire amount of controllablemedium 34 at working space 36 and allowing for wear and tear ofabsorbent element 46, the present invention avoids the need to provide alarge quantity of medium, and the associated seals, bearings andcontaining devices of the prior art. Accordingly, the present inventionreduces the tight tolerances formerly needed on all components.

Absorbent element 46 is preferably fixed to one of the relatively movingmembers 38, 40 to ensure that it remains disposed in the working space36. According to a preferred embodiment, absorbent element 46 isadhesively bonded using a pressure sensitive adhesive to one of themembers. One preferred absorbent element 46 is polyurethane foam havinga pressure sensitive adhesive on one side. The foam may be readilyattached to one member by the adhesive. Alternatively, absorbent element46 may be shaped so that it is held in place by the structure of themember, for example, a tubular shaped foam material may be fitted arounda member as a sleeve. Finally, absorbent element 46 does not need tofill working space 36.

Referring to FIGS. 2A-2B, magnetic-field generating device 42 preferablycomprises at least one coil 48 formed of an electrically-conducting wirewound about a retainer 50, such as a plastic bobbin or spool. Thewindings of wire forming coil 48 are wound such that energizing the coilwith electricity produces an induced magnetic field, represented by fluxlines 44, that intersects magnetically-controlled medium 34. The inducedmagnetic field is proportional to the electric current supplied toenergize the coil 48, such as from the output signal of computer system28 and number of turns of wire. The wire forming coil 48, as will berealized by one skilled in the art, may be selected from a broad rangeof electrically-conducting materials, depending on the range of thedesired magnetic field strength, the range of desired electricalcurrent, space constraints, and desired operating voltage. For example,wire may comprise materials such as copper, aluminum, gold, silver andthe like. Similarly, the gauge of the wire and the number of windingswithin coil 48 are dependent upon the application, and can be determinedby methods known by one skilled in the art.

Magnetic field generating device 42 may be adjacent first member 38 orsecond member 40, but is preferably disposed within a recess 52, such asannular recess shown, formed within one of members (shown within firstmember 38 in FIG. 2B). The lead wires 53 (FIG. 2A) connecting to coil 48are connected to controller 28, which provides a signal 66′ (shown indetail in FIG. 1A) to energize the coil, as is discussed in furtherdetail below. Because the wires 53 connecting coil 48 may be mounted toa moving member, there may be a need to restrict the movement of thatmember in order to avoid breaking the wire by excessive stretching,bending or rotation of the wires. Alternatively, means may be providedto enable a connection to controller 28 even with excessive linear,rotational, pivotal or curvilinear movement. For example, a slip-ringconnector, a wire take-up reel, and a coiled wire may be utilized toallow for great amounts of movement while maintaining a reliableconnection. These alternatives are generally more costly, however, andthus are not as desirable for a cost efficient haptic interface system.

Referring to FIG. 1A, magnetically-controllable device 24 is preferablyintegrated with haptic interface device 26 and sensor 32 to comprise ahaptic interface unit (as represented by the dashed line 55). The hapticinterface unit 55 may additionally comprise a control unit 54 and/or asignal amplification device 56, as will be discussed in more detailbelow. The haptic interface unit 55 may further comprise a protectivehousing or shell within which each of the above-mentioned components aremounted.

Haptic interface device 26 may be any device in operable contact withoperator 22. Operator 22 maneuvers haptic interface device 26 to controland respond to the interactive program processed by the computer systemof controller 28. A suitable haptic interface device 26 may comprise asteering wheel, a joystick, a steering yoke, a crank, a foot pedal, aknob, a mouse, a lever, a seat, a motor bike frame, a jet ski frame, adownhill ski frame, amusement part ride, and any other device inoperable contact with operator 22.

Sensor 32 is in communication with haptic interface device 26 foridentifying a detected position within any of the plurality of positionswithin which the haptic interface device may be moved. Sensor 32provides a variable input signal to controller 28 based on the detectedposition. Because haptic interface device 26 may be continually moving,sensor 32 must quickly provide controller 28 with an updated detectedposition of the haptic interface device 26 in order to allow thecontroller 28 to update its output signal to provide the operator withtactile sensations as computed by the interactive program. Ideally,sensor 32 provides control unit 54 with a continuous signal that variesin proportion to the movement of the detected position of the hapticinterface device 26.

Suitable sensors may comprise a potentiometer, such as Clarostat 10K ohmpotentiometer, an optical encoder, such as a Clarostat Series 6000optical rotary encoder, or any type of rheostat or variable resistor.For example, sensor 32 may be mounted on a shaft connected to a steeringwheel to detect the rotation of the steering wheel. Also, more than onesensor 32 may be required to detect complex movements of hapticinterface device 26. For example, if haptic interface device 26 is ajoystick, one sensor 32 may be connected to a component of the joystickto determine a movement in the x-direction, while another sensor 32 maybe connected to another component of the joystick to determine amovement in the y-direction. In this example, the x-direction sensor andthe y-direction sensor may each send a variable input signal tocontroller control unit 54.

Control unit 54 receives the variable input signal from sensor 32 andprovides a variable output signal to magnetically-controllable device24. As discussed above, there is a continual feedback loop between thecontrol unit 54 of controller 28 and haptic interface device 26, andhence between host computer 58, magnetically-controllable device 24 andsensor 32. The interactive program being processed by host computer 58uses the variable input signal from sensor 32 as an input to theinteractive program. Based upon this input, the host computer 58 furtherprocesses the control program to determine the variable output signal tosend to magnetically-controllable device 24. Returning to the previouslypresented example of operator 22 controlling a computer system, in sucha computer system, the control or interactive program within hostcomputer 58 processes an input signal from sensor 32. From this, thehost computer 58 determines a semi-active resistance force required frommagnetically-controllable device 24 in order to coordinate what operator22 is viewing on display 30 with what the operator is feeling throughhaptic interface device 26 in order to simulate tactile sensations. Hostcomputer 58 sends a signal to display 30 to update the displayed image,and concurrently sends an output signal to magnetically-controllabledevice 24. The output signal sent to magnetically-controllable device24, for example, may be an electric current having a value in proportionto a resistance force desired to be felt by operator 22. Thus, inattempting to move haptic interface device 26, operator 22 feels thechange in resistance force applied by magnetically-controllable device24 through the haptic interface device, thereby providing force feedbacksensations.

While, in general, controller 28 receives a variable input signal fromsensor 32 and generates a variable output signal tomagnetically-controllable device 24, a number of different componentsmay be involved in the signal transactions. Controller 28 may comprisehost computer 58, and may further include control unit 54 andamplification device 56 to communicate with haptic interface device 26.Host computer 58 typically includes an input/output 60 forsending/receiving electrical signals, a processor 62 and a memory 64 forrespectively processing and storing electrical signals representative ofan interactive program, for example. A suitable host computer 58 is, forexample, a personal computer such as a IBM, Compaq, Gateway or othersuitable computer capable of processing the appropriate information.Input/output 60 may comprise a plurality of serial and/or parallelcommunication ports, such as RS-232 type ports, and high-speedbi-directional communication channels like the Universal Serial Bus(USB). Processor 62 may comprise an Intel Pentium® or other suitablemicroprocessor. Memory 64 may comprise Random Access Memory (RAM) andRead-Only Memory (ROM), as well as other well-known types of memory. Asone skilled in the art will appreciate, depending upon the particularapplication, there is a broad range of personal computers,input/outputs, microprocessors and memories that may be utilized withthe present invention.

For example, host computer 58 may send output signal 66 comprising anelectric current proportional to a desired resistance force to beapplied to haptic interface device 26. Output signal 66 may be receivedby control unit 54 for additional processing. Control unit 54 may be amicrocomputer having an input/output 68, a processor 70, such as adigital signal processor (DSP), for processing electrical signals, amemory 72 for storing electrical signals, and/or firmware 74 that storesand processes electrical signals, where the electrical signals arerepresentative of a local interactive program or inputs from otherdevices with system 20. Input/output 68, microprocessor 70, and memory72 may be substantially similar to those described above for hostcomputer 58, however, the capabilities of control unit 54 may be morelimited to reduce cost. Control unit 54 processes output signal 66 fromhost computer 58 and provides a modified output signal 66′.

Additionally, control unit 54 may locally process signals or portions ofsignals directly received from components within system 20. For example,control unit 54 may receive variable input signal 76 from sensor 32 andsearch the signal for portions that may be processed locally beforepassing the input signal on to host computer 58 as modified variableinput signal 76′. Also, control unit 54 may provide modified inputsignal 76′ to place input signal 76 in a format that may be understoodor processable by host computer 58. Further, control unit 54 may receiveinput signal 78 from haptic interface device 26, such as a signal from abutton or trigger 79 on the haptic interface device. Input signal 78 maybe a signal that requires a reflex-like response, such as the firing ofa gun. Rather than burdening host computer 58 with processing thesetypes of signals, which may be very frequent, control unit 54 providesthe processing capability. Input signal 78 may be completely processedby control unit 54, thereby advantageously reducing the processingburden on host computer 58. Thus, the use of control unit 54 increasesthe efficiency of system 20 by performing force feedback computations inparallel with the force feedback computations being performed by hostcomputer 58 in running the interactive program.

Similarly, control unit 54 may receive concise high-level commands,comprising all or a portion of output signal 66, to be processed locallywithin the control unit 54. These high-level commands may representsimple, semi-active, variable resistance force sensations that may beeasily processed locally by control unit 54. Thus, in effect, controlunit 54 provides a parallel processing capability to host computer 58 tomaximize the overall efficiency of system 20.

Modified variable output signal 66′ provided by control unit 54 mayrequire further processing before being received bymagnetically-controllable device 24. Modified output signal 66′ may bereceived by amplification device 56, for example, to boost the level ofmodified output signal 66′ to provide amplified output signal 66″.Modified output signal 66′ may be a variable signal of low electricalcurrent that is not sufficient to properly energize coil 48 to produce amagnetic field to the desired strength to provide the desired resistanceforces. To solve this problem, amplification device 56 proportionallyincreases the strength or amperage of modified output signal 66′ to alevel sufficient to properly energize coil 48. Thus, amplificationdevice 56 advantageously allows lower strength signals to be processedwithin system 20, thereby saving cost by requiring less heavy dutycomponents and less power, before boosting the signal to a levelrequired to properly energize magnetically-controllable device 24.

As mentioned above, control unit 54 and amplification device 56 may be apart of computer system 28 or the haptic interface unit or they may beseparate components within system 20. Those skilled in the art willrealize that the various components described above may be combined innumerous manners without affecting the operability of the system.Similarly, some of the components, such as control unit 54 amplificationdevice 56, may not be required if their function can be adequatelyperformed by other system components, such as host computer 58. Thus,variation of the above-described configuration of system 20 iscontemplated by the present invention.

Haptic interface system 20 comprises two closely coupled, interactivefunctions: a sensory input function and a force output function. Thesensory input function tracks the operator's manual manipulation of thehaptic interface device, feeding sensory data to the controllerrepresentative of those manipulations. The force output functionprovides physical tactile feedback to the operator in response tocommands from the host computer. These two functions are intertwined inthat the sensory input function generally varies in response to theforce output function, and vice versa. In other words, the operator'smanipulations of the haptic interface device are affected by the appliedresistance forces, or force feedback, and the applied resistance forcesare dependent upon the manipulations of the operator. Thus, hapticinterface system 20 involves a very complex and continual interaction.

Returning again to the example of the computer system operator 22, inoperation, host computer 58 runs an interactive program, such as a game,using processor 62 to generate a video signal 80 received by display 30.Video signal 80 is an electrical signal used to generate an image,corresponding to an event occurring within the game, on display 30.Operator 22 responds to the event by moving haptic interface device 26,such as a steering wheel or a joystick, in conjunction with the viewedevent. Sensor 32 sends variable input signal 76 comprising trackinginformation representing the position of the wheel or joystick tocontrol unit 54. Control unit 54 may respond to the information byprocessing the information locally, and by forwarding the information,or a modified form of the information, as a modified variable inputsignal 76′ to host computer 58. Even when processing informationlocally, control unit 54 may provide modified variable input signal 76′to host computer 58 and/or display 30 to update the generated image ofthe event to correspond with the latest input.

Host computer 58 receives modified variable input signal 76′ fromcontrol unit 54 and inputs that information into processor 50 that isrunning the interactive game. Host computer 58, based on the processingof modified input variable signal 76′, updates the image of the eventgenerated on display 30 and provides a variable output signal 66 inproportion to a resistance force to be felt by operator 20 in moving thewheel or joystick. Variable output signal 66 may be modified by controlunit 54 and amplified by amplification device 56 before reachingmagnetically-controllable device 24 as amplified variable output signal66″. The strength of amplified variable output signal 66″ varies inproportion to a desired magnetic field strength, and hence resistanceforce, as computed by host computer 58 to coordinate with theinteractive program.

Again referring to FIGS. 1B, 2A and 2B, variable output signal 66″thereby energizes coil 48 within magnetically-controllable device 24 toproduce a magnetic field. The magnetic field is applied across workingspace 36, affecting the shear strength of magnetically-controllablemedium 34 contained within absorbent element 46. The affect on the shearstrength of medium 34 creates a semi-active, resistance force betweenfirst 38 and second 40 members, which is connected to haptic interfacedevice 26. As a result, operator 22 feels the changed resistance forcethrough haptic interface device 26 during attempted movements of thehaptic interface device. Thus, haptic interface system 20 providesopposing force feedback sensations, or resistance forces, to operator 22maneuvering haptic interface device 26 to simulate a realistic feel. Forexample, the following feels may be simulated: jolting blasts, rigidsurfaces, viscous liquids, increased gravity, compliant springs, jarringvibrations, grating textures, heavy masses, gusting winds, and any otherphysical phenomenon that can be represented mathematically and computedby controller 28.

The following comprises a number of different embodiments employing theteachings of the present invention. Where elements are substantially thesame as those discussed above, they are given the same referencenumeral. Based on the variety of mechanisms utilized by variousmanufacturers to reduce the movement of a haptic interface device intomanageable and measurable components, such as movements in anx-direction and a y-direction, numerous configurations of hapticinterface systems utilizing the teachings of this invention may beemployed. Thus, these examples are not intended to be limiting, but areexemplary of the teachings of the present invention to numerousembodiments of haptic interface systems.

In general, the movement of a haptic interface device 26 is eitherlinear or rotary, which includes partial rotation or curvilinear motion.Similarly, a magnetically-controllable device 24, as mentioned above, iscapable of providing opposing variable resistance force to either linearor rotary movements, including partial rotation or curvilinear motion.To control the movements of the haptic interface device 26, themagnetically-controllable device 24 must somehow be linked to the hapticinterface device 26. As such, the linking mechanisms typically translatethe following types of movement from the haptic interface device 26 tothe magnetically-controllable device 24: linear to linear; linear torotational; rotational to rotational; and rotational to linear. Hence,the configuration of the haptic interface unit may vary, and theconfiguration of the magnetically-controllable device 26 may vary,depending on: the mechanisms used to resolve the movement of the hapticinterface device 26; space constraints; resistance force and/or torquerequirements; and cost constraints. Therefore, the teachings of thepresent invention may be applied to a plurality of differentconfigurations with equal success.

Referring to FIG. 3, one embodiment of the present invention compriseshaptic interface unit 55 having a magnetically-controllable device 24that is adapted to apply resistance forces to haptic interface device 26through drive mechanism 92. In FIG. 3, the interface device is asteering wheel which is shown for use in FIG. 1C in a vehicle. In suchan application magnetically controllable device 24 is a rotary brake andmonitor 30 displays vehicle operating information. Drive mechanism 92may be driven by an operator 22 (See FIG. 1C.) in operable contact withhaptic interface device 26, such as the steering wheel shown. Sensor 32is in rotary contact with drive mechanism 92 to determine and report theposition of the drive mechanism, which corresponds to the position ofhaptic interface device 26. Haptic interface unit 55 further comprises aframe 94 to which magnetically-controllable device 24 and sensor 32 arefixedly mounted, and to which drive mechanism 92 is movably mounted,such as with a low friction element like bearings, bushings, sleeves orthe like. The sensor senses rotational displacement of of the steeringwheel.

Drive mechanism 92 comprises a disc 96 fixedly attached to shaft 98.Disc 96 is configured to engage magnetically-controllable device 24 andsensor 32 during rotation of steering wheel 26. Disc 96 may comprise around disc, or only partial segments of a round disc if limited rotationis desired. Disc 96 may comprise peripheral gear teeth as shown or ahigh-friction surface to engage magnetically-controllable device 24 andsensor 32.

Referring to FIG. 4a, the magnetically-controllable device 24 of FIG. 3is shown in cross section and comprises a pair of first plate members 38disposed adjacent to both sides of rotating, disc-like second member 40.Annular ring member 100, comprising a high magnetic permeabilitymaterial, forms a peripheral wall around second member 40 and combineswith first member 38 to form a housing 99. Fastening means 102 may beemployed in a plurality of places to hold together the components of themagnetically-controllable device 24. Fastening means 102 may comprisesscrews, clamps, bonding or any other method for holding together thecomponents of device 24. Further holding means may fasten the device 24to the frame 94.

An absorbent element 46 which is preferably a disc shaped ringcontaining magnetically-controllable medium 34 is sandwiched in twoplaces between first member 38 and second member 40. Magnetic-fieldgenerating device 42, including coil 48 wound about retainer 50 isdisposed adjacent first member 38 and second member 40 at the peripheryof magnetically-controllable device 24. The coil 48 is connected by leadwires 53 to the controller 28 (FIG. 3). Thus, a magnetic fieldrepresented by flux lines 44 is produced upon the energization ofmagnetic-field generating device 42.

Shaft 104 extends through and is fixedly secured to the second member 40and interconnects at one end to disc 96 (FIG. 3) through engaging member106, such as a wheel, gear or pinion. Engaging member 106 is fixedlyattached to shaft 104, such as by a force fit, a set screw, a adhesiveor welded bond, a pin, and any other suitable method of holding theengaging member in a fixed relationship to the shaft. Engaging member106 may have peripheral gear teeth or a high friction surfacecomplementary to the periphery of disc 96. A first bearing member 108 isdisposed on shaft 104 between engaging member 106 and second member 40.First bearing member 108 allows for the rotation of shaft 104 andsupports the shaft against radial loads relative to the first member 38.A suitable bearing member 108 may comprise a roller bearing, a sleeve orwasher of a low friction material such as nylon or Teflon®, or othersuitable mechanisms. A second bearing member 110 is disposed at theother end of shaft 104, on the opposing side of second member 40. Secondbearing member 110 provides radial support for shaft 104 and secondmember 40. A suitable bearing member 110 may comprise a thrust bearing,a sleeve or washer of a low friction material such as nylon or Teflon®,and other similar mechanisms.

Disc 96 and engaging member 106 are sized so that the ratio of theirdiameters is in a range of ratios that allows magnetically-controllabledevice 24 to provide a suitable amount of resistance force. Similarly,the ratio of the radius of disc 96 and the radius of engaging member 112fixedly connected to shaft of sensor 32 (FIG. 3) similar to engagingmember 106, must be calibrated to insure proper system performance.

FIG. 4b illustrates an alternate embodiment of magnetically controllabledevice 24 b which may be used in place of the device 24 of FIG. 4a. Inthis device, the shaft 104 b is radially supported in a U-shaped firstmember 38 b by bearings 108 b, 110 b. Engagement member 106 b engagesdisc member 96 of FIG. 3. The device 24 b attaches to the frame 94 byfastening means 102 b received through the ends of first member 38 b andthrough spacer 90. Disc-shaped second member 40 is locked by means of apress fit on shaft 104 b and rotates therewith. Localized absorbentelements 46 b are positioned on either side of second member 40 b andare preferably open celled polyurethane foam adhesively secured to theinsides of first member 38 b. Magnetically-controllable medium 34 b isretained by the elements 46 b. Upon energizing the magnetic fieldgenerator 42 b by providing electrical current to lead wires 53 b whichinterconnect to a coil 48 wound about the first member 38, a magneticflux 44 is created which is carried by the first member 38 b andtraverses the elements 46 b retaining the medium 34 b. This energizationchanges the rheology of the medium and creates a resistance force thatacts to prevent relative rotation between the members 38 b, 40 b therebyproviding resistance forces to the operator 22.

Referring to FIGS. 5-7b, another embodiment of the present inventioncomprises haptic interface unit 155 (control unit and amp not shown forclarity) utilizing a pair of magnetically-controllable devices 24 asdescribed above with reference to FIG. 4a. FIG. 1D illustrates thejoystick located in a vehicle where monitor 30 displays operatingcharacteristics of the vehicle. Alternatively, the brakes shown in FIG.4b may be used. For clarity, some of the components of device 155 arenot shown or shown separately, such as a pair of sensors 32 one of whichis shown in FIG. 7b. In this embodiment, each magnetically-controllabledevice 24 is adapted to apply resistance forces to haptic interfacedevice 26, such as a Gravis Pro joystick, through drive mechanism 122.

Drive mechanism 122 is in communication with haptic interface device 26through first 124 and second 126 plates that translate in a y and xdirection, respectively, responsive to the movement of the hapticinterface device. Each plate 124, 126 comprises a groove 128 and 130(FIG. 7) within which post 132 at the base of haptic interface device 26moves. The post 132 is secured to, or integral with, the interfacedevice 26 and moves with the interface device 26 about pivot 125. Themovement of post 132 within the grooves 128, 130 resolves the motion ofhaptic interface device 26 into its respective y-direction andx-direction components. Each plate 124, 126 transfers its linear motion,corresponding to the y or x directions, through first 134 and second 136wheels, respectively, which are fixedly attached to respective shafts138, 140. As such, the linear motion of plates 124, 126 is converted torotational motion in shafts 138, 140.

The rotational motion of shaft 138, 140 is then provided to eachmagnetically-controllable device 24 through respective engaging members106 in contact with respective third 142 and fourth 144 wheels, fixedlyattached to shafts 138,140. Further, each shaft 138, 140 has one endrotatably mounted in housing 146 and the opposite end rotatably mountedin panel 148. Housing 146 and panel 148 may be manufactured from avariety of materials, such as plastics or metal. Legs 150, typicallyprovided in four places, fixedly attach housing 146 and panel 148 andprovide a base upon which interface unit 155 stands. Thus, the pair ofmagnetically-controllable devices 24 are able to apply semi-active,variable resistance forces to oppose movement of haptic interface device26, such as a joystick, through drive mechanism 122.

It should be recognized that the housing 146 and panel 148 are merelyexemplary and any suitable housing and support means may be utilized.Further, depending upon the torque achievable in the respective devices24, the shafts 138 may be directly attached to devices 24. Moreover,other types of power transmission or gearing arrangements other thanspur gears may be utilized, such as bevel gears, helical gears, wormgears and hypoid gears. Springs (not shown) may be provided that connectbetween the haptic interface device 26 and the housing 146 to springbias the device in all directions and provide a return spring function,i.e., center the device.

Signals representative of the x and y motions are provided by respectivesensors 32 including arm 82 received in recesses 84 in the plates 124,126. Movement of the plates 124, 126 in the respective x and ydirections rotates the respective arms 84 of sensors 32, which arepreferably rotary potentiometers. This produces a signal correspondingto x and y motion which is processed by the control system to provideforce feedback signal to the respective device 24. The one or morebuttons or triggers 79 a, 79 b shown send additional signals to thecontrol unit 54 (FIG. 1).

FIG. 8 illustrates another embodiment of haptic interface unit 255 withthe cover portion of housing removed for clarity. The unit 255 comprisesa haptic interface device 26 pivotally moveable to cause movements inthe respective x and y directions or any combination thereof. Suchmovements of the device 26 cause respective movements in rack and pinionassemblies 86 x, 86 y. interconnected to respective magneticallycontrollable devices 24 x, 24 y. Assemblies 86 x, 86 y include a rack 87and pinion 106. The rack 87 includes projections 91 which slide in slots89 formed in the housing portion 246 thereby restricting motion to onlyalong the z direction. A spherical ball 93 mounted on extension 83 isreceived in guide 95 formed in the haptic interface device 26.

Movement of the device 26 in the x direction, for example, pivots thedevice below flange 97 about a pivot point (not shown) and causes guide95 to engage ball 93 to move rack 87 x in the z direction. Likewise,movement of device 26 in the y direction causes guide 95 to engage ball93 and move rack 87 y in the z direction. Any z movements of racks 87 x,87 y cause teeth 85 on the outer surface of racks 87 x, 87 y to engageteeth on pinions 106 x, 106 y. This rotates respective shaft 104 x, 104y (not shown) and fixedly secured second members 40 x, 40 y ofmagnetically controllable devices 24 x, 24 y.

Sensors 32 x, 32 y generate signals representative of the x and ymovements through utilizing rack assemblies similar to that described inFIG. 8b where a moving component of sensor 32 x, 32 y is interconnectedto the rack (e.g. 87 s). Coils 48 x, 48 y are selectively energized toproduce a magnetic flux in U-shaped first members 38 x whose legsstraddle the second member 40 x, 40 y. A magnetically controlled medium(not shown) is included between the respective legs and the secondmember 40 x, 40 y as shown in FIG. 4b and is preferably retained in anabsorbent member as described therein. The control system 28 in responseto position signals from leads 53 x′, 53 y′ controls the effectiveresistance generated by devices 24 x, 24 y by supplying signals to leads53 x, 53 y.

Referring to FIGS. 9 and 10, another embodiment of amagnetically-controllable device 24 comprises a first member 38 having au-shaped body that receives second member 40 at its open end 160. Anabsorbent element 46 is disposed in each working space 36 between firstmember 38 and second member 40. Each absorbent element 46 containsmagnetically-controllable medium 34. Magnetic-field generating device 42is disposed about closed end 162 of second member 40, and creates amagnetic field through magnetically-controllable medium 34, asrepresented by flux lines 44, upon energization by controller 28 (FIG.1). Magnetic-field generating device 42 is connected to controller 28 bywires 53. As indicated by the arrows on second member 40 (FIG. 9), therelative movement between the second member and first member 38 may belinear, rotational or curvilinear. Thus, this embodiment ofmagnetically-controllable device 24 provides resistance forces to opposelinear, rotational or curvilinear relative movements between firstmember 38 and second member 40.

The magnetically-controllable device 24 in FIGS. 9 and 10 may beintegrated into haptic interface unit 55 (FIG. 3), by mounting thedevice to frame 94 and having disc 96 act as second member 40 much thesame as is shown in FIG. 4b. In this case, disc 96 needs to comprise amagnetically soft material, as discussed above in reference to secondmember 40. Similarly, a pair of devices, like themagnetically-controllable device 24 in FIGS. 9 and 10, may be integratedinto haptic interface unit 155 (FIGS. 5-7b). This may be accomplished ina joystick, for example, by mounting the devices to housing 146 andhaving first and second translating plates 124 and 126 act as a secondmember 40 in each device. Of course, plates would need to bemanufactured from a magnetically permeable material.

Finally, referring to FIG. 11, another embodiment ofmagnetically-controllable device 24 comprises first member 38, having acurved, annular ring-shaped body, and second member 40 having apivotable, disc-like body. Magnetic-field generating device 42 is anannular shaped member at the periphery of second member 40, adjacent tofirst member 38. Magnetically-controllable medium 34 is included in achamber 35 and in the working space 36 between first member 38 andsecond member 40. Magnetic-field generating device 42 creates a magneticfield through magnetically-controllable medium 34 in working space 36,as represented by flux lines 44, upon energization by controller 28 (notshown). Magnetic-field generating device 42 is connected to controller28 by wires 53.

An operator 22 (FIG. 1D) in operable contact with haptic interfacedevice 26, such as a joystick, moves second member 40 fixedly attachedshaft haptic interface device 26. Pivot member 172 opposes device 26 onthe other side of second member 40. Pivot member 172 preferablycomprises a post having a ball-shaped end. Pivot member 172 is securedto magnetically-controllable device 24 by bottom plate 174, which alsois fixedly attached to first member 38. Similarly, top member 176 may beconnected to first member 38 to further reinforcemagnetically-controllable device 24. Thus, as one skilled in the artwill recognize, the teachings of the present invention may beimplemented in a variety of haptic interface units to provide resistanceforces to oppose the motion of haptic interface device 26 in hapticinterface system 20. Moreover, it will be recognized that a wide varietyof magnetically controllable devices may be utilized herein. Forexample, the magnetorheological fluid devices described in commonlyassigned U.S. Pat. Nos. 5,816,372, 5,711,746, 5,652,704, 5,492,312,5,284,330 and 5,277,281 may be used.

Although the invention has been described with reference to thesepreferred embodiments, other embodiments can achieve the same results.Variations and modifications of the present invention will be apparentto one skilled in the art and the following claims are intended to coverall such modifications and equivalents.

What is claimed is:
 1. A haptic interface system comprising: a hapticinterface device movable by an operator in at least one direction ofdisplacement, the haptic interface system providing resistance forces tothe haptic interface device; a controller for receiving a variable inputsignal and providing a variable output signal, said controller adaptedfor running a program that processes said variable input signal and inresponse derives said variable output signal; and amagnetically-controllable device that receives said variable outputsignal and provides said variable resistance force in proportion to saidvariable output signal, said magnetically controllable device comprisinga volume of a magnetically controllable medium, the variable resistanceforces being provided by changing the rheology of the magneticallycontrollable medium in response to said output signal to therebydirectly control the ease of movement of the haptic interface device,said variable resistance forces being provided to resist displacement ofthe haptic interface device by the operator in at least one direction ofdisplacement of said device.
 2. The haptic interface system as recitedin claim 1, wherein said haptic interface device comprises a steeringdevice.
 3. The haptic interface system as recited in claim 2 whereinsaid steering device is for steering a vehicle or machine.
 4. The hapticinterface system as recited in claim 1, wherein said haptic interfacedevice comprises a joystick.
 5. The haptic interface system as recitedin claim 2, wherein said haptic interface device comprises a steeringwheel.
 6. The haptic interface device as claimed in claim 2 wherein thesteering device is a steering yoke.
 7. The haptic interface system asclaimed in claim 1 wherein said haptic interface device comprises alever.
 8. The haptic interface system as claimed in claim 1 wherein themagnetically controllable medium is magnetorheological powder.
 9. Thehaptic interface system as recited in claim 1, wherein saidmagnetically-controllable device comprises: a magnetic-field generatingdevice energizable by said variable output signal to provide a variablestrength magnetic field; a first member adjacent to said magnetic fieldgenerating device; a second member adjacent to said magnetic fieldgenerating device and connected to said haptic interface device; andwherein said magnetically-controllable medium is located between saidfirst member and said second member.
 10. A haptic interface system asrecited in claim 9, further comprising an absorbent element disposedbetween said first member and said second member, said absorbent elementcontaining said magnetically-controllable medium.